1. Field of the Invention
This invention relates to a rock drill or machine drill for drilling a plurality of bores of slit-like shape in continuously arrayed bores and, more particularly, to a rock drill which comprises a plurality of drilling rods disposed in such a manner that they can drill several arrayed bores by a percussive force which is imparted by a single percussive means such that it is able to reduce the energy consumed as well as to miniaturize the size of the percussive means.
2. Description of the Prior Art
In digging works, such as tunnelling or the like, and where there are one or more dwellings, previously built facilities or buildings adjacent to the construction site, it is usual that construction relying on blasting is bound by regulations on the time of blasting, the number of the times of blasting, the amount of explosive to be used in one blasting operation in view of the environmental problems due to vibrations and noise caused by blasting, and for the sake of precaution to avoid the possible scattering of stones and crushed rocks. Accordingly, it is inevitable that such blasting take place at several times rather than in a single blasting operation.
Moreover, at a construction site where use of explosive is prohibited, digging work, relying on a rock breaker or breakers is sometimes utilized. However, such digging work is inefficient in digging hard rock stratum.
Rock drilling by means of arrayed bore drilling can be effectively applied to these crushing operations. Even where there is no particular regulation for blasting, drilling of such arrayed bores along the outer periphery of the cross section to be cut followed by blasting utilizing the arrayed bores as a free surface or surfaces, will provide beneficial effects with less amount of explosive, together with better surface finish, as compared with the angle cutting method, by virtue of the fact that it is possible to make use of the tensile breakage of the rock under drilling.
There has been proposed one type of rock drill for drilling arrayed bores for use in these conditions wherein a plurality of rock drills are disposed along a straight line and each rod of the rock drills carries bits capable of drilling arrayed bores or one in which a plurality of rock drills are disposed in an arrangement shifted from one after another in a lengthwise direction (refer to Japanese Laid-Open Patent Publication No. 57-116893).
In the former case, however, since the spacing between the centers of adjacent bits becomes larger than the transverse width of the rock drill to be used, the diameter of the bit has to be made larger so as to form arrayed bores. This naturally requires larger drilling energy.
In the latter case, since the rock drills are shifted one after another in a lengthwise direction, the spacing between the centers of two adjacent bits cannot be made smaller than half of the sum of the transverse width of the rock drill and the rod diameter. Accordingly, it is impossible to greatly reduce the drilling energy of the device, although the spacing has been made slightly smaller than that of the former case. In addition, since both of the rock drills of the prior art mentioned above are of the type which includes a plurality of rock drills, the percussion means become larger in size together with an increase in the number of pipings from the power source which impairs the operability of the device and brings about troublesome problems in maintenance.
This invention aims to obviate such problems encountered in rock drills for drilling arrayed and continued bores as mentioned above. Another object of the invention is to provide a rock drill which can remarkably reduce the required drilling energy.
A further object of the invention is to provide a rock drill having a percussion member smaller in size than previously utilized and which is better in operability. A still further object of the present invention is to provide a rock drill which can carry out non-explosive rock crushing work with high efficiency so as to prevent any environmental nuisance, such as vibrations and noise.